This invention relates generally to inkjet printers. More specifically, the present invention relates to focused ink drop detection of inkjet printer nozzles.
Inkjet printing mechanisms, e.g., printers, photocopiers, facsimile machines, etc., typically implement inkjet cartridges, often called xe2x80x9cpensxe2x80x9d to shoot drops of ink onto a sheet of print media, e.g., paper, fabric, textile, and the like. Some inkjet printing mechanisms carry an ink cartridge with an entire supply of the ink back-and-forth across the sheet. Other inkjet print mechanisms, known as xe2x80x9coff-axisxe2x80x9d systems, propel only a small ink supply with the printhead carriage across the print zone, and store the main ink supply in a stationary reservoir, which is located off-axis from the path of the printhead travel. Typically, a flexible conduit or tubing is used to convey the ink from the off-axis reservoir to the printhead cartridge.
Pens typically have a printhead that includes very small nozzles on an orifice plate through which the ink drops are fired. The particular ink ejection mechanism within the printhead may take on a variety of different forms as known to those skilled in the art, such as those using piezoelectric or thermal inkjet technology. To print an image, the printhead is scanned back-and-forth across a print zone above the sheet, with the pen shooting drops of ink as it moves. By selectively firing ink through the nozzles of the printhead, the ink is expelled in a pattern on the print media to form a desired image (e.g., picture, chart, text and, like). The nozzles are typically arranged in one or more linear arrays along the printhead. If more than one, the two linear arrays are typically located side-by-side on the printhead, parallel to one another, and substantially perpendicular to the scanning direction. Thus, the length of the nozzle arrays defines a print swath or band. That is, if all the nozzles of one array were continually fired as the print head made one complete traverse through the print zone, a band or swath of the ink would appear on the sheet. The height of this band is known as the xe2x80x9cswath heightxe2x80x9d of the pen, the maximum pattern of ink which can be laid down in a single pass.
The orifice plate of the printhead has a tendency to pick up contaminants, such as paper dust, and the like, during the printing process. Such contaminants may adhere to the orifice plate either because of the presence of ink on the printhead, or because of electrostatic charges. In addition, excess dried ink can accumulate around the printhead. The accumulation of either ink or other contaminants can impair the quality of the output by interfering with the proper application of ink to the print media. In addition, if color pens are used, each printhead may have different nozzles which each expel different colors. If ink accumulates on the orifice plate, mixing of different colored inks (cross-contamination) can result during use which may lead to adverse affects on the quality of the resulting printed product. Furthermore, the nozzles may become clogged, particularly if the printheads are left uncapped for a relatively long period of time. For at least these reasons, it is desirable to clear the printhead orifice plate of such contaminants on a substantially routine basis.
In this respect, servicing operations are typically performed on the nozzles prior to, during, and after completion of the performance of a printing operation. To accomplish the servicing operations, inkjet printing mechanisms typically possess a service station located along the scanning direction to perform a plurality of servicing operations on the nozzles, e.g., collecting spit ink, capping the nozzles, and wiping the orifice plate.
The manner and form of the servicing operations are typically controlled by a servicing protocol that uses a drop detector to determine whether any of the nozzles are operating in an improper manner, e.g., nozzle outs, paper crashes, and the like. As an example, a servicing operation may be triggered when the drop detector determines that a nozzle in a printhead is clogged or otherwise improperly ejecting ink. The servicing protocol may control the printheads of a printer mechanism to travel over the drop detector at certain times before, during and after performance of a printing operation. Typically, once the printheads are maneuvered over the drop detector, each of the nozzles contained in each of the printheads is tested. Although this type of complete nozzle testing is typically beneficial to the quality of the printed output, the amount of time required to perform the ink drop detections on all of the nozzles (e.g., known printheads may include two rows of 524 nozzles) typically negatively impacts throughput, i.e., amount of time required to print a plot.
In accordance with one aspect, the present invention relates to a method of focused ink drop detection. In the method, a first drop detection is performed on a plurality of nozzles. Each of the nozzles is characterized into at least one of a plurality of groups, based upon the results of the first drop detection. In addition, each of the groups corresponds to a predetermined nozzle condition. The categorization of each of the nozzles is stored in a memory. Further, a second drop detection is performed on a first group of nozzles. In addition, the characterization of the nozzles may be predicated upon the available historical data of each of the nozzles obtained during previous drop detections.
In accordance with another aspect, the present invention pertains to an apparatus for operating a printing mechanism having at least one printhead, in which each of the printheads has a plurality of nozzles. The apparatus includes a controller operable to control the plurality of nozzles to fire a set of ink drops into a drop detector. The drop detector is configured to determine a characteristic of the ink drops fired from each of the nozzles to thereby determine a condition of each of the nozzles. The apparatus also includes a memory configured to store the conditions of the nozzles, in which the nozzles are characterized and stored in terms of their conditions, and in which the nozzles are grouped in terms of their conditions. The controller is further operable to a control at least one group of the nozzles to fire another set of ink drops into the drop detector.
According to yet another aspect, the present invention relates to a computer readable storage medium on which is embedded one or more computer programs. The one or more computer programs implement a method for operating a printing mechanism having a printhead, in which the printhead has a plurality of nozzles. The one or more computer programs include a set of instructions for performing a first drop detection on the plurality of nozzles. The one or more computer programs also include a set of instructions for categorizing each of the nozzles into at least one of a plurality of groups, based upon the results of said first drop detection, in which each of the groups correspond to a predetermined nozzle condition. The one or more computer programs further includes a set of instructions for storing the categorization of each of the nozzles in a memory and performing a second drop detection on a first group of nozzles.
In comparison to known printing mechanisms and techniques, certain embodiments of the invention are capable of achieving certain aspects, including some or all of the following: (1) time savings in performance of ink drop detections; (2) ink savings during performance of ink drop detections; (3) substantial optimization of the ink drop detection process; (4) substantial conformance of the ink drop detection operations based upon user preferences. Those skilled in the art will appreciate these and other benefits of various embodiments of the invention upon reading the following detailed description of a preferred embodiment with reference to the belowlisted drawings.